Process for obtaining alkaline-earth-metal sulphides from alkalineearth-metal sulphates



Patented Apr. 24, 1928 UNITED STATES 1 1,667,423 PATENT OFFICE.

TEEOIDOR LICHTENIBERGER, OF HEILIBRONN, AND KONRAD FLOR, OF BUCKEBURG,

. GERMANY.

PROCESS FOR OBTAINING ALKALINE-EARTH-METAL SULPHIDES FROM ALKALINE-- EARTH-METAL SULPHATES.

Nb Drawing. Application filed March 4, 1926, Serial No. 92,334, and in Germany Ma a, 1925.

It has already been proposed to obtain sulphur from alkalineea1'tl1-metal sulphates by dissolvin'gjthe samein alkali-metal chloride in a molten condition. In this process, for

5 the purpose, of producing alkaline-earth metal sulphide, carbon is employed either in the form of solid coal or in the form of reducing gases;

It has no'w been discovered that solid coal 0 does not (admit of being mixed well with the melt. The-coal experiences owing to the degasification an upward drive and burns very quickly in the'surface without being utilized I for the reduction; The reduction is therefore only incomplete and requires a considerable expenditureof coal.

The process forming the subject-matter of the present invention is distinguished from the known'process by the fact that the carbon is employed in the form of coke and that after the reduction a separation of the alkali-metal chloride from the alkaline-earthmetal sulphide is effected by sedimentation, whereupon the alkali-metal chloridev is drawn ofi' above, while the alkaline-earthmetal sulphide is converted in known manner by treatmentwith vapour or acid into alkaline-earth metal oxide or alkaline-earthmetal salt and hydrogen sulphide.

The coke admits of being mixed well with the melt and exerts a reducing action very quickly.

The invention isfurther based upon the discovery that the alkaline-earth-metal sul phides in the fused mas's admit of being sharpl separated from the alkali-metal chlori es by sedimentation. Consequently after the reduction only a clarification of the melt is necessary. The alkali-metal chloride 40 may be drawn oii above and employed afresh for dissolving alkaline-earth-metal sulphates. u The alkaline-earth-metal sulphide obtained however is further treated,

for the purpose of obtaining the" hydrogen.

sulphide, in the manner mentioned above.

For the preparationof sodium sulphide and potassium sulphide from the corre- Spending sulphates by means" of coal and common salt the use of coke has already been suggested. In the treatment of alkaline-1 earth-metal sulphates, however, coke has not hitherto been employed.

Ma esium chloride is preferably melted up with the melt which consists of alkalimetal chloride and alkaline-earth-metal sulphide. By this means the conversion of the alkaline-earth-metal sulphides into alkalineearth-metal chlorides is accelerated. 1 The addition of the magnesium chloride may take place either before or after the reduction of the melt with coke.

Magnesium chloride has already been employed in the production of hydrogen sulphide in the wet way. This process however is costly and leads to the pollution of .the waste waters.

The process may for example be carried out by introducing almost dehydrated magnesium chloride into the alkalimetal chloride melt containing the reduced alkalineearth-metal sulphates. Large quantities of hydrogen sulphide gas then escape with the elimination of magnesium oxide, while from the alkaline-earth-metal sulphides insoluble inthe melt, alkaline-earth-metal chlorides are evolved which are readily soluble in the molten alkali-metal chlorides.

The evolution of hydrogen sulphide may be increased and accelerated if water vapour is passed into the melt.

In the manner described above a volatile melt free from alkaline-e'arth-metal. sulphides is very quickly obtained which consists of alkali-metalchlorides and alkalinev earth-metal chlorides. In this melt the magnesium oxide is very quickly deposited, so

that it can easily be removed.

. If the melt of alkali-metal chlorides and alkaline-earth-metal chlorides freed .from

magnesia and still containing only theexcess coke is utilized afresh for dissolving and reducing alkalineeearth-metal sulphates, the

working' process can firstly be made continuous and'secondlythe defects which are inherent in the wet process and which consist in the costly production. of alkaline-earth metal chlorides-by evaporation or in the pollution of ri'versbythe waste waters can-be eliminated in a-technical simple manner.

Owing to the fact that the magnesia. is

Instead of sodium chloride it is possible to employ other alkali-metal or other alkalineearth-metal salts or mixtures of such salts for melting up the alkaline-earth-metal sulphates. In this case salts must be selected which are fusible in an anhydrous condition and which do not exert any decomposing action when in a molten condition upon alkaline-earth-metal sulphates.

It has been discovered that the alkalineearth-metal sulphates can easily be dissolved to a clear thinly liquid melt not only in molten sodium chloride but also in other molten alkali-metal or alkaline-earth-metal salts as Well as in molten mixtures thereof. Those alkali-metal or alkaline-earth-metal salts can be used which are particularly fusible in an anhydrous condition and which when in a molten condition exert no decomposing action upon alkaline-earth-metal sulphates. Particularly suitable are the sulphates of the alkali metals as well as the fluorides of the alkali and alkalineearth-mtals either alone or'mixed with other alkali-metal or alkaline earth-metal salts.

If for example fiuorspar is employed as a melting bath there are preferably mixed with it for the purpose of lowering the melting point alkali fluorides 0r alkaline-earthmetal chlorides. The same advantage is also obtained if an intimate mixture of alkali-metal or alkaline-earth-metal fluorides or alkaline-earth-metal chlorides is melted up with the alkaline-earth-metal sulphates as its melting point lies far below the melt ing point of the individual components.

The fusible masses produced in this manner from alkaline-earth-metal sulphates with alkali-metal or alkaline earth salts or with mixtures thereof are then further treated for obtaining the alkaline-earth-metal sulphate sulphur in the same manner as has been described above. Coke is'stirred into the melt as a result of which the alkalineearth-metal sulphate is reduced to alkalineearth-metal sulphide and the latter, by blow ing in steam or acid, is further decomposed into alkaline-earth-metal oxid e or the corresponding alkaline-earth-metal salt and bydro en sulphide which can then be further wor ed up in a known manner to sulphur or sulphur compounds.

If alkali-metal or alkaline-earth-metal salts are employed which singly or mixed in the melting bath split off acid when steam is blown in, after the reduction of the alkaline-earth-metal sulphates is terminated the alkaline-earth-metal sulphide obtained is decomposed by blowing in steam into alkalineearth-metal salt and hydrogen sulphide as the acid that forms under the action of steam on the melting bath acts in a'nascent condition upon the alkaline-earth-metal sulphide.

"What we claimjs 1. Process for obtaining sulphur compounds from alkaline-earth-metal sulphates, comprising dissolving the sulphate in molten sodium chloride, adding coke to obtain alkaline-earth-metal sulphide, separating the alkali-metal chloride from the alkalineearth-metal sulphide by sedimentation and drawing off the alkali-metal chloride above.

2. Process for obtaining sulphur compounds from alkahne-earth-metal sulphates, comprising dissolving the sulphate in molten sodium chloride, adding magnesium chloride and coke to the melt of alkali-metal chloride and alkaline-earth-metal sulphate and thereby obtaining alkaline-earth-metal sulphide and magnesium oxide, separating the alkalimetal chloride from the alkaline-earthmetal sulphide by sedimentation and drawing off the alkali-metal chloride above.

3. Process for obtaining sulphur compounds from alkalineearth-metal sulphates, com rising dissolving the sulphate in molten alka i-metal salts which are fusible without water and do not decompose alkaline-earthmetal sulphates when in a molten condition, adding coke to obtain alkaline-earth-metal sulphide, separating the alkali-metal salts from the alkaline-earth-metal sulphide by sedimentation and drawing ofi the alkalimetal salts above.

4. Process for obtaining sulphur compounds from alkaline-earth-metal sulphates, comprising dissolving the sulphate in molten alkaline-earth-metal salts which are fusible without water and do not decompose alkaline-earth-metal sulphates when in a molten condition, adding coke to obtain alkalineearth-metal sulphide, separating the alkaline-earth-metal salts from the alkalineearth-metal sulphide by sedimentation and drawing off the alkaline-earth-metal salts above.

5. Process for obtaining sulphur compounds from alkaline-earth-metal sulphates, comprising dissolving the sulphate 1n a mixture of molten alkali-metal and alkalineearth-metal salts which are fusible without water and do not decompose alkaline-earthmetal sulphates when in a molten condition, adding coke to obtain alkaline-earth-metal sulphide, separating the alkali-metal and alkaline-earth-metal salts from the alkalineearth-metal sulphide by sedimentation and drawing off the alkaline-earth-metal salts above.

6. Process for obtaining sulphur comwater and do not decompose alkaline-earth-- metal sulphates when in a molten condition, adding magnesium chloride and coke to the melt of alkali-metal salts and alkaline-earthmetal sulphate and thereby obtaining alka line-earth-metal sulphide and magnesium oxide, separating the alkali-metal salts from the alkaline-earth-metal sulphide by sedimentation and drawing off the alkali-metal salts above.

7 Process for obtaining sulphur compounds from alkaline-earth-metal sulphates, comprising dissolving the sulphate in molten alkaline-earth-metal salts which are fusible without water and do not decompose alkaline-earth-metal sulphates when in a molten condition, adding magnesium chloride and coke to the melt of alkaline-earth-metal salts and a-lkaline-earth-metal sulphate and thereby obtaining alkaline-earth-metal sulphide and magnesium oxide, separating the alkaline-earth-metal salts from the alkalineearth-metal sulphide by sedimentation and drawing oil the alkaline-earth-metal salts above.

8. Process for obtaining sulphur compounds from alkaline-earth-metal sulphates,

comprising dissolving the sulphate in a mixture of molten alkali-metal and alkalineearth-metal salts which are fusible without water and do not decompose alkaline-earthmetal sulphates when in a molten condition, adding magnesium chloride and coke to the melt of alkali-metal salts and alkaline-earthmetal salts and alkaline-earth-metal sulphate and thereby obtaining alkaline-earthmetal sulphide and magnesium oxide, separating the alkali-metal and alkaline-earthmetal salts from the alkaline-earth metal sulphide by sedimentation and drawing off THEOD OR LICHTENBERGER. KONRAD FLOR. 

